Estudo do gene MUC1 e características de sanidade e produção em vacas de leite

Abstract

The present study aimed to identify possible relations between the polymorphism of the MUC1 gene and the productive traits of dairy cows, especially regarding those related to the health of the mammary gland. Blood samples from Jersey and Gir animals from Pelotas - RS, Aceguá - RS and Capão do Leão - RS (Jersey), Caxias do Sul - RS and Nova Odessa – SP (Gir) were used. The DNA samples were extracted from the biological material with the aid of the saline method. The genotypes were obtained through the polymerase chain reaction (PCR) technique, and observed on agarose gel. PCR products of Gir breed samples were submitted to sequencing by the method of Sanger. The numbers of repeats were estimated, and allele and genotype frequencies were calculated. In the Jersey breed, mixed models were used to obtain associations between the genotypes of the MUC1 gene and the characteristics of milk production in kilos (PL), fat percentage (GORD), lactose percentage (LAC), protein percentage ) and somatic cell score (ECS). Three alleles were identified in both breeds, measuring 800 (allele 1), 950 (allele 2) and 1050 (allele 3) base pairs (pb) (allele 3) in Jersey and 1000 (allele A), 1050 (allele B) and 1266 bp (C allele) in the Gir breed. The number of tandem repeats estimated was 6 (allele 1), 8.6 (allele 2) and 10.2 (allele 3) and 13 (allele A), 14 (allele B) and 17 (allele C), for the Jersey and Gir respectively. In the Jersey breed the allele 3 was the most frequent in the four farms studied, and the allele 2 was found to be of rare occurrence. The genotype 3/3 had the highest occurrence in all farms, except in farm 4 where its presence was equal to genotype 3/1, which in turn was the second most frequent in the other farms. Corroborating the low allele frequency of allele 2, no homozygous animals were found. The allele A showed predominance in the studied Gir populations, making up 88% of the total alleles found. Alleles B and C presented less occurrence. A total of 77% of the animals were identified as homozygous for the A allele, whereas only 2% of the animals presented homozygous of the C allele, and none presented the homozygous genotype with the B allele. The heterozygous AC genotype was the second largest occurring in 15% of the animals. The association analyzes performed did not present significant results, and further studies may be necessary in order to clarify associations more effectively.